The present invention relates to novel pharmaceutical compositions of a fibrinolytic agent. More specifically, the present invention relates to frozen liquid and lyophilized compositions of fibrolase and, separately, of xe2x80x9cnovel acting thrombolyticxe2x80x9d (NAT), as well as methods for the production and use thereof.
In general, polypeptides are marginally stable in the aqueous state and undergo chemical and physical degradation resulting in a loss of biological activity during processing and storage. Another problem encountered in aqueous solution in particular is hydrolysis, such as deamidation and peptide bond cleavage. These effects represent a serious problem for therapeutically active polypeptides which are intended to be administered to humans within a defined dosage range based on biological activity.
To reduce the degradation of polypeptides, water-based pharmaceutical compositions are generally kept refrigerated or frozen until ready for use. As an alternative, the process of freeze-drying is often employed to stabilize polypeptides for long-term storage, particularly when the polypeptide is relatively unstable in liquid compositions. A lyophilization cycle is usually composed of three steps: freezing, primary drying, and secondary drying; Williams and Polli, Journal of Parenteral Science and Technology, Volume 38, Number 2, pages 48-59 (1984). In the freezing step, the solution is cooled until it is adequately frozen. Bulk water in the solution forms ice at this stage. The ice sublimes in the primary drying stage, which is conducted by reducing chamber pressure below the vapor pressure of the ice, using a vacuum. Finally, sorbed or bound water is removed at the secondary drying stage under reduced chamber pressure and an elevated shelf temperature. The process produces a material known as a lyophilized cake. Thereafter the cake can be reconstituted prior to use.
The standard reconstitution practice for lyophilized material is to add back a volume of pure water (typically equivalent to the volume removed during lyophilization), although dilute solutions of antibacterial agents are sometimes used in the production of pharmaceuticals for parenteral administration; Chen, Drug Development and Industrial Pharmacy, Volume 18, Numbers 11 and 12, pages 1311-1354 (1992).
Lyophilization is considered one of the best ways to remove excess water from polypeptide solutions. The freeze-drying process may yield products that are stable and amenable to handling for long-term storage. Lyophilized products can be stored at room temperature and are therefore easier to handle and distribute to a wider geographic market, such as foreign markets where refrigeration may not be available.
Excipients have been noted in some cases to act as stabilizers for freeze-dried products; Carpenter et al., Developments in Biological Standardization, Volume 74, pages 225-239 (1991). For example, known excipients include polyols (including mannitol, sorbitol and glycerol); sugars (including glucose and sucrose); and amino acids (including alanine, glycine and glutamic acid).
In addition, polyols and sugars are also often used to protect polypeptides from freezing and drying-induced damage and to enhance the stability during storage in the dried state. In general, sugars, in particular disaccharides, are effective in both the freeze-drying process and during storage. Other classes of molecules, including mono- and di-saccharides and polymers such as PVP, have also been reported as stabilizers of lyophilized products.
The present invention relates to stable pharmaceutical compositions of fibrolase and xe2x80x9cnovel acting thrombolyticxe2x80x9d (NAT), some of which are liquid compositions suitable for storage in the frozen state, and others of which are suitable for lyophilization.
Because of the fibrinolytic properties of fibrolase and NAT, the compositions of this invention are useful to lyse blood clots in vivo and may be administered therapeutically for such a purpose.
For purpose of this invention, the term xe2x80x9cNATxe2x80x9d refers to the metalloproteinase having fibrinolytic activity which is characterized by SEQ ID NO: 1. The NAT polypeptide is encoded by the cDNA molecule of SEQ ID NO: 2, although any DNA molecule of variant sequence encoding the same polypeptide may be used for expression and manufacture in accordance with methods which are referred to hereinbelow.
Fibrolase is a known metalloproteinase which has been described in the scientific and patent literature; dee Randolph et al., Protein Science, Cambridge University Press (1992), pages 590-600, and European patent Application No. 0 323 722 (Valenzuela et al.), published Jul. 12, 1989. Typically, the fibrolase employed in the compositions of this invention will be of SEQ ID NO: 3, which is encoded by the cDNA molecule of SEQ ID NO: 4 (or variants thereof encoding the same amino acid sequence).
Fibrolase and NAT are to be distinguished from other therapeutic agents for the treatment of blood clots in vivo, such as urokinase, streptokinase and tPA which are plasminogen activators. Unlike these other agents, fibrolase and NAT act directly on the clot to degrade both fibrin and fibrinogen.
The pharmaceutical compositions of this invention will contain, in addition to a therapeutically effective amount of fibrolase or NAT, a zinc stabilizer and, optionally, a bulking agent with or without other excipients in a pharmaceutically-acceptable buffer which, in combination, provide a stable, frozen or lyophilized product that can be stored for an extended period of time.
In one of its aspects, the present invention provides a freezable liquid medicinal composition comprising fibrolase or NAT, a water soluble zinc salt, a citric acid buffer, optionally an additional stabilizer selected from the group consisting of water soluble calcium salts, and optionally a bulking agent (for example, mannitol). A surfactant, such as Tween 80 (BASF, Gurnee, Ill.), may also be added to increase freeze-thaw stability. Tris buffer (Sigma, St. Louis, Mo.) or another buffer with a buffer capacity above pH 7.0 may be added to stabilize the pH at or above pH 7.4.
In another aspect of the present invention, the pharmaceutical composition can be a lyophilizable or lyophilized pharmaceutical composition comprising fibrolase or NAT, a zinc stabilizer (e.g., water soluble zinc salt), and a citric acid buffer, with or without other excipients (e.g., bulking agent such as mannitol, glycine, or the like). The lyophilized composition may also contain a disaccharide sugar, such as sucrose or trehalose, as a lyoprotectant. A surfactant, such as Tween 80, may be added to protect against lyophilization stresses on the metalloproteinase (fibrolase or NAT). The pH will ideally be maintained at pH 8.0xc2x10.5, using a suitable buffer with a PKa in this range (for example, Tris).
The invention also comprises a method for preparing a lyophilized composition, comprising the steps of (i) mixing fibrolase or NAT with a buffer and a water soluble zinc salt, as well as any desired optional ingredients, and (ii) lyophilizing this mixture.
In addition, the invention provides a kit for preparing an aqueous pharmaceutical composition, comprising a first container having the aforementioned lyophilized composition and a second container having a physiologically acceptable solvent therefor.
Still another aspect of this invention comprises a method comprising the steps of reconstituting the lyophilized composition and administering the reconstituted composition to a patient in need of blood clot lysis.